Process of producing aluminum nitrid.



H. L. DUNCAN.

PROCESS OF PRODUCING ALUMINUM NITRlD.

APPLICATlON F|LED OCT. 12. I9|6| Patented 00. 2,1917.

1 so as to impingemn the fa 124L834. I Continuation inypa rt orattenuation SerialNo 587,419, filed Qctober1'7; 1910. Thi I I I 12,1916.Serie1No.'125,158.

c To all whom it may c ohc ern:

' centralized,vluminousflame wit UNITED T T TENT mamnfinity M;

Be itknown that LHARRY'L. DUNCAN, a citizen of the United States, nowresiding at Mahwah, Bergen county," New Jersey, have madea certa n newand useful Invent1on- Relating-to Processes of Producing Aluminum Nitricl "of which the following is a. specification, taken inconnection Withthe accompanying di awing, which forms 1 part I ofthe same. 'Th sapplicatlon 1s a continuaz-;

tion in partthat is, contains subjeot natter taken in from .my"copending "application 587 419, filed'October 17, 1910.'

ally to'proo- This inyenti'on relates especl esses for producing nitiids of aluminum and other metals by supplying the hot carbonaceousfalunii'nous charge at materiah for instance, to a rotatingtreating kilnthrough which it is, gradually fed and simultaneeusiy' agitated. Thematerial maybe heated by a I min the kiln which may be producedbysupply-ing to the discharge 'en'd of'the kiln a lowfpressure diffuseheatingyj'et or, stream of luminous flame producer gas vand injecting:substantially axially intolthe kiln a high pressure jet of air or'other oxidizer engaging said heating -stream i'andi forming therewith asubstantially centralized heating flame transmitting heat I to the kilnwalls and" material, While kept from undesirable contact therewith'bythelayer of de a 'wa1l ga ses in engagement withithef kiln walls and Ina-xterial. A nitrogenous treat.

jet of hot into the kiln ig agitated t the: same tion' on the producergas may; be injecte charge oi'"material an moon-y; withoutexertmguhdsflable kiln walls and forthis,purpose the jet ma be of highpressu're and discharged fnom flattened nozzle substantially inlinewiththe bank otmaterial. Af nitrogenous reducing atmosphere ispreferably maintained in the lower lldl' 'Of the treating kiln at aslight excess of pressure ahoye' the" outside 311' to nnnimizeingressthereo-f and the combustible gases: discharged fro'm' thetreating kiln may'l he used to heat: the charge of material as''bynburning them in a?- p'reheating k111i;

An illustrative "form of apparatusfor can. rying out thISPIQCBSS-iSShOWQ 1n a-" so1ne"- What. d agrammatic way in the accompanyeSpecification of Letters Pate aiit;

*- ing drawing in Whihh l glure through thie treating ake with whichathe d ischarge' Y sired, provided en the e packingring's washersoniinembeis 5fiseeur'e ble elements of .these ykilnn:gasesi; ihay-.be-f

discharge throat 12 an 'tat'ed ihany desired wa chamber 14: and stack .c

withii nthe' portf,9"and;up1bl'1e the desired pressure a suitable fencerblower 23 "connectedicimithtr ingly-"Ipromoted." 3

section and Fig.

along the "line 22 of Fig, rotary kiln 1- may he p my, preferably inert,I

able materialtand .i' ."1th'nia c onstllfl charge throa 2; thekilnibeing meniited an rotated any desiredwwvayz cooperates, ispreterahlywtightl I ycon nee therew th, a suitable han 4 ilngi'i-fl decoopei ating with suitable metallic Dr? to the sons to make a tight kilnjoin The upperencl'ot' the" kilma dicatedgbewithe bott' y ypepinasimilarly connectedf'tvith th whousing through the fi ange Wand packingg-Rva'sher or connections 8; The kiln"gases fromitlns". treating kiln 1may be:.disoharged'itlinoug the port 9 after pa'ssing up thro'ughjth 1 yj i i passage 10 in the, hoilsing landrthe combiisti this kiln maycooperate-With 5 v'snitabie'stf fsuffieien I to maintain thedesireditstaek ltaf t i the kiln and'draw inadditidhx throng the"ii'sualeki ln jointf-l'fic matromote -tl1 heating action in thi klln.The,

discharged from-this pre" ating' N erably slides-{past a j mounted onthe supper :and %;p1(3 .l1t1ng leakage pfgas from the? assag l9 Siii.ablehir'injecting gp-ipespgQi w "the 6 2 this way the eloeity-of h"asesxpas.

ing thi oughy the portQegintovt pinkie-1 kilnrll;maybeincreased t thedesin e. ea tentgand combiistion' the through, the regulatin arranged inthe casing and operated at the desired speed by the pulley 27. Thealuminous material is gradually feddown the preheating kiln by itsrotation and becomes quite highly heated therein so as to be hot whendischarged into the treating kiln 1. Additional carbonaceous materialma'j; be conveniently incorporated with the charge entering the treatingkiln by feeding such pulverized carbon or the like from the hopper 28and connected conveyer casing 29 by the feed screw 30 driven at thedesired speed by the pulley 31. This carbonaceous material thus becomesmixed with the aluminous portion of the charge as the materials enterthe treating kiln and becomes intimately mingled therein as they arecontinually ag tated and simultaneously fed down through the kiln in theform of an inclined bank of material on its ascending side. The material60 entering the treating zone at the lower end of the kiln is thussubstantially homogeneous and has been still more highly igeated in theupper part of the treating iln.

It is desirable to maintain within the suchproducer gas to the lower endof the treating kiln in sufiicient amounts, a slight excess of pressuremay be maintained within the kiln above that of the outside air whichtends to prevent air being drawn into the kiln through the variousopenings in the hood. A treating jet of such nitrogenous gas is alsopreferably injected into the discharge end of the kiln in such way as toimpinge on the falling agitated charge of material and effect thedesiredreactions therein, which of course develo considerable heat Wherealuminum nitrid is formed. It is desirable to inject the treating gas inthe form of a flat treating jet having its flat side substantially inline with the bank of material extending up through the kiln so as toimpin e upon the material throughout a considerab e treating zonewithout exerting undesirable action on the kiln walls which may withgood results be coated with a protective layer of the forming material.This fiattened treating jet 35,, may as indicated, be discharged at anangle of some thirtydegrees or so to the adjacent kiln walls or bank ofmaterial on which it impinges, and

this gas jet may be discharged from a suitable nozzle 36 in the hoodconnected with a pipe 37 leading, from the producer 39 and provided witha regulating valve 38 so that the hot treating ases may be supplied atthe desired high ressure. This producer should, of cours be operated soas to secure a sufficiently high temperature in the treating jet todefinitely effect the desired chemical reactions in the material in thekiln and for this purpose the producer may be blown with air without theuse of steam or similar cooling means and the producer gas may of coursebe still more highly heated by well known regenerator or other heatingdevices before injecting it into the kiln. In order to preliminarilyheat the treating kiln and maintain it and thematerial fed therethroughat the desired high temperature, a luminous heating flame may withadvantage be employed, preferably in a sub stantially centralizedposition within the kiln so as to transmit'heat by radiation to thematerial and kiln walls without destructive action thereon, and thussupply at least a large part of the heat required to bring the charge upto the combining temperature, although if desired additional heat can ofcourse be supplied as by electric heating elements arranged in the kilnwalls for instance. A substantially centralized jet of air or otheroxidizing material together, if desired, with suspended particles ofoil, powdered coal or other fuel .for combustion therewith may beinjected into the kiln by any suitable injecting devices so as toproduce in this way a luminous heating flame which is kept substantiallyor largely out of contact with the kiln walls or material: because ofthe interposed reducing atmosphere in the kiln. If desired, a suitablehigh pressure air jet may be substantially axially injected into thekiln to burn in the reducing atmosphere therein and transmit heat to thekiln walls and material without undesirable contact therewith. For somepurposes it is desirable to supply to the kiln in connection with suchair jet a diffuse low pressure jet or stream of luminous flame produceror other gas. Such a low pressure heating stream of gas may be injectedthrough the flaring gas port 46 connected with the pipe 47 from theproducer-l9 and having the controlling valve 48 therein. This produceris preferably operated to give luminous flame gas which may be enrichedby incorporating hydrocarbon oils or similar material therewith. A highpressure directive air jet may be injected into the kiln along the line50 through the air nozzle 51 supplied with air from the fan or blower43, the pressure or velocity of the issuing jet being regulated by thevalve 52 so as to be in'the neighborhood of one to two ounces equivalentpressure on entering the kiln so as to give the resulting flame asulliciently centralized position. The rough kiln walls tend to holdpractically stationary the layer of gases in contact with them so thatthese dead wall gases tend to prevent undesirable contact between theheating flame, preferably of highly luminous character. and the kilnwalls and material. Anothelair jet teena e connected to the fan orblower 43 and sup plied with air, at the desired pressure and in theproper amounts through the regulating valve 42. This heating jet isadapted to cooperate with the gas passing through the nozzle 36 which isprovided with a relieved portion 40 at its upper'discharge end and underthese conditions the gas pressure should be suificiently low so as toinject through this nozzle a diffuse gas jet and prevent such forcibleimpingement upon the material as occurs under normal working conditions.

The treatingu-kiln may be put in operation by admitting sufiicientproducer gas thereto to substantially displace the air therein and thenpreferably supplying luminous flame producer gas to the kiln insufficient amounts so as to produce luminous heating flame therein inconnection with the air jet's, These jets may be ignited'in any desiredway as by the electric igniter 56 which may be inserted through asuitable opening 54 so as to bring the sparking terminals 55'adjacentthe air jet to cause ignition when high tension electricity is passedthrough the-wires 57. Asuitable bushing 58 of course normally closes theopening 54 around this igniter and the opening is kept closed during thenormal operation of the kiln, preferably by a door having a transparentwindow or peep hole to allow observation of the kiln interior. Theheating flame produced under these conditions may have the shape andlocation indicated as 45 and the layer of dead wall'gas 61 tends toprevent-contact between this flame and the kiln walls or material. WVhenthe material has beensufliciently heated the nitrogenous reducing gasesin the kiln react with the a luminous carbonaceous charge forming nitridand this action may be promoted by injecting the treating jet 35 ofnitrogenous producer gas into engagement with the agitated material.This promotes the formation of a highly heated treating zone in thelower end of the kiln sothat the conversion of the material passingtherethrough is ef fected to the desired extent before this material isdischarged through the chute 33 plying the hot carbonaceous aluminouscharge of material to a rotating treatlng kiln, 1n agitating and feedingsaid charge through said kiln in the form of an inclined bank ofmaterial, in supplying through the discharge end of said kiln a lowpressure diffuse heating stream of luminous flame producer gas, ininjecting substantially axially into said kiln a high pressure jet ofair engaging said heating stream and form-' ing therewith a luminoussubstantially centralized heating flame kept from undesirable contactwith the material and kiln walls by the dead wall gases whiletransmitting heat thereto, in maintaflining in the lower end of saidkiln a nitrogeneous reducing atmosphere at a-pressure above that of theoutside air, in injecting through the discharge end of said kilnafiattened high pressure nitrogenous t'reatingjet of hot producer gas toimpinge on the falling agitated charge of material and convert the sameinto nitrid without exerting undesirable action on the kiln walls and inburning the combustible gases discharged from said kiln to heat thecharge of material supplied thereto.

2. The process of producing aluminum nitrid which consists in supplyingthe carbonaceous aluminous charge of material to a rotating treatingkiln and thereby agitating and feeding said charge through said kiln, insupplying through the discharge end of said kiln a low pressure diffuseheating stream of luminous flame producer gas, in injectingsubstantially axially into said kiln a high pressure jet of air engagingsaid heating streamand forming therewith a luminous substantiallycentralized heating flame transmitting heat to the material and kilnwalls, in maintaining in the lower end of said kiln a nitrogenousreducing at- ,charge end of said kiln a flattened high pressurenitrogenous treating jet of hot producer gas to impinge on the materialand convert the same into nitrid without exerting destructive action onthe kiln walls.

3. The process of producing metallic nitrid which consists in supplyingthe carbonaceous charge of material to a rotating treating kiln andthereby agitating and feeding said charge through said kiln, insupplying through the discharge end of said kiln a low pressure diffuseheating stream of producer gas, in injecting substantially axially intosaid kiln a jet of air engaging said heating stream and formingtherewith a substantially centralized heating flame transmitting heat tothe ma terial and kiln walls, in maintaining a nitrogenous reducingatmosphere in the lower end of said kiln and in injecting a highpressure treating jet of hot producer gas into said kiln to impinge onthe material therein and convert the same into nitrid go withoutexerting destructive action on the kiln walls. a

4. The process of producing metallic nitrid which consists in supplyingthe carbonaceous charge of material to a treating kiln, in agitating andfeeding said charge through said kiln in the form of a bank of material,in injecting into said kiln a flattened high pressure nitrogenoustreating jet of combustible gas to impinge on the agitated bank ofmaterial and convert the same into nitrid without exerting destructiveaction on the kiln walls and in injecting into said kiln a jet of airengaging said treating gas and forming therewith a heating flametransmitting heat to said material and kiln walls without undesirableaction thereon.

5. The process of producing metallic nitrid which consists in supplyingthe charge containing reducing material to a treating kiln, in agitatingand feeding said charge through said kiln in the form of a bank ofmaterial, in injecting a narrow nitrogenous treating jet intoimpingement with the agitated charge of material to convert the sameinto nitrid without exerting undesirable destructive action on the kilnwalls, in maintaining a nitrogenous reducing atmosphere in the lowerpart of said kiln and in heating said material.

6. The process of producing metallic nitrid which consists in supplyingthe charge containing reducing material to a treating kiln,

in agitating and feeding said charge through said kiln in the form of abank of material, in injecting a hot small area nitrogenous treating jetinto impingement with the agitated charge of material to convert thesame and in maintaining a nitrogenous reducing atmosphere about saidcharge of material in the discharge end of said kiln.

7. The process of producing aluminum nitrid which consists in supplyingthe carbonaceous aluminous charge of material to a treating kiln, inagitating and feeding said charge through said kiln in the form of abank of material, in injecting a narrow nitrogenous treating jet intoimpingement with the agitated charge of material to convert the samewithout exerting undesirable destructive action on the kiln walls, inmaintaining a reducing atmosphere in contact with said convertedmaterial at the discharge end of said kiln and in injecting an oxidizingjet into said kiln to form a heating flame therein transmitting heat tothe material and kiln walls without undesirable action thereon.

8 The process of producing aluminum nitrid which consists in agitatingthe charge of material in a treating kiln, in maintaining a nitrogenousreducing atmosphere in contact with said material at one end of saidkiln, in injecting into said kiln an oxidizing jet to form a heatingflame in said kiln transmitting heat to said material withoutdestructive action thereon and in injecting a jet of nitrogenoustreating gas into impingement with said charge of material to convertthe same into aluminum nitrid.

9. The process of producing aluminum nitrid which consists in supplyingthe carbonaceous charge of material to a rotating treating kiln andthereby agitating and feeding said charge through said kiln, insupplying combustible nitrogenous treating gas to the discharge end ofsaid kiln to maintain therein a nitrogenous reducing atmosphere at apressure at least equal to that of the adjacent outside atmosphere, ininjecting substantially axially into said kiln a jet of air engagingsaid gas and forming therewith a substantially centralized luminousheating flame transmitting heat to the man terial and kiln walls withoutundesirable contact therewith and in bringing said material while highlyheated into engagement with said nitrogenous treating gas to convert thesame intoraluminum nitrid.

10. The process of producing aluminum nitrid which consists in supplyingthe charge containing reducing material to a treating kiln, in agitatingand feeding said charge through said kiln in the form of a bank ofmaterial, in injecting a narrow nitrogenous treating jet intoimpingementwith the agi tated charge of material to produce nitridtherein without exerting undesirable destructive action on the kilnwalls, in main taining a nitrogenous reducing atmosphere in the lowerpart of said kiln and in heating said material.

11. The process of producing aluminum n1trid which consists in agitatingand feed ing the charge of aluminous material through a rotatingtreating kiln, in maintaming a nitrogenous reducing atmosphere 1ncontact with said material in the treating zone of the kiln, insupplying heat to the material 'from a substantially centralizedluminous flame in the kiln,.in' injecting a high pressure jet of hotnitrogenous gas to impinge on the heated material in said treating zoneat an angle of more than fif teen degrees to the adjacent kiln walls toconvert the'material into aluminum nitrid and in preventing substantialingress of oxidizing gases into the lower end of the kiln adjacent thekiln walls or material.

12. The process of producing aluminum nitrid which consists in agitatingand feeding the charge of aluminous. material through a rotatingtreating kiln, in maintaining a nitrogenous reducing atmosphere incontact with said material in the treating zone of the kiln, insupplying heat to the material from a substantially centralized luminousflame in the kiln and in'injecting hot nitrogenous gas to impinge on theheat ed material in said treating zone at an angle of more than fifteendegrees to the aoljacent kiln Walls to convert the material into alu-'minum nitrid.

13. The process of producing aluminum nitrid which consists in agitatingand feed ing the charge of aluminous material through a rotatingtreating kiln, in maintaining a nitrogenous reducing atmosphere incontact With said material in the treating zone of the kiln, insupplying heat to the material and in injecting hot nitrogenous gas toimpingeon the heated material in said treating zone at an angle of morethan fifteen degrees to the adjacent kiln Walls to convert the materialinto aluminum nitricl.

14. The process of producing aluminum, nitrid which consists inagitating and feeding a charge of aluminous material through a rotatingtreating kiln, in producing luminous heating flame in said kiln toradiate heat to the kihi walls and material, Without undesirable contacttherewith, in maintaining a nitrogenous reducing atmosphere in contactwith the heated material in the treating'zone of the kiln and ininjecting a jet of hot nitrogenous gas into said kiln to impinge on theheated material in the treating zone at an angle of at least as much astwenty degrees to the adjacent kiln Walls to convert the material intoaluminum nitrid;

15. The process of producing aluminum nitricl which consists inmaintaining a nitrogenous reducing atmosphere in contact with thealnminous material in the treating zone, in supplying heat to thematerial and in injecting-a high pressure jet of hot nitrogenous gas toimpinge on the heated material in said treating zone at an angle of morethan twenty degrees to convert the material into a1 uminurn nitrid.

16. The process of producing aluminum nitrid which consists inmaintaining a nitrogenous reducing atmosphere in contact with thealuminous material in the treating zone, in supplying heat to thematerial and in injecting nitrogenous gas to impinge on the heatedmaterial in said treating zone to convert the material into aluminumnitritl. I

HARRY L. DUNCAN. Witnesses:

J'Essn B. KAY, Cnannns EBERHART.

